DTXF-xxx Narrow band single channel FSK transmitter The DTXF-xxx series, a narrow band module with 12.5KHz channel spacing, is a high performance transmitter designed for use in industrial & commercial applications requiring long range, high performance and reliability. The DTXF transmitter is ideally suitable with long range applications at low power consumption, typically lower than 25mA at 10mW output power. Also a built-in SMA connector enables just to screw-in Cellution's standard antenna without any antenna matching process. And the rugged RF shielding will block unexpected noises from in-out circuitary. The DTXF-xxx supports South Korean ISM band, 424.7MHz, 447.3MHz and Japanese 429MHz as well as European 433.92MHz. DRXF & DTXF w/o shield can DTXF w/o shield can FEATURES Direct FM modulation include: under 2.5kHz Frequency Deviation Transmitting power 5~10mW(10dBm under) Low current consumption : 25mA@ 3.0~5.5V Long distance communication: Up to 1 mile (1.6Km) in line of sight. Operating temperature: -20 ~ 65 APPLICATIONS Remote control system Telemetry system Wireless home automation Security alarm system Paging system Wireless sensor network system Frequency Allocation PART NUMBER Country FREQUENCY CH Remarks CRFDTXF-433.92 European ISM 433.92 MHz 1 <=10mW CRFDTXF-424 Korea 424.7000 MHz 1 <=10mW CRFDTXF-447 Korea 447.3000 MHz 1 <=10mW
PIN DESCRIPTIONS Name I/O ANT O RF output terminal (the 50Ohm SMA type connector) (ANT) O RF Ground terminal Connected to the of the RF Connector I Power supply terminal DC 3.0 5.5V I TX enable terminal To enable TX(active), connect to Pull high or DC 3.0~5.5V TX_DATA I Transmitted data input terminal H: 2.8V, L: 0V I Ground Terminal TX Part Specification Parameter Specification Remark Communication method Half-Duplex Operating frequency Refer to Frequency allocation Transmitting method Direct FM Modulation Oscillation type Crystal Oscillator Frequency stability +/-4ppm +/-8ppm 0 to + 55 C -20 to + 65 C Operating Temperature range -20 to + 65 C Operating Voltage range 3.0 5.5V DC Current consumption 25mA typical Dimensions 18*33*12mm Including Shield Case & I/F Pin Data rate 4800 bps max. Channel Spacing 12.5kHz Transmitting Power 9mW Antenna impedance 50 Ohm Frequency Deviation 2.3k+/-0.3kHz Adjacent channel leakage power -40dBc Channel spacing 12.5kHz Spurious Emission -60dBc <1GHz
DIMENSION DTXF Dimension : 37*17.6*11mm Unit : mm Right Angle type SMA Connector 6.3 Shield Case 1.15 D=3.2pi 2.25 Fixing screw 2.4 4.55 DTXF-XXX D=1.0pi 11.1 17.6 0.55 2.54 4 3 2 1 TX_DATA 6.6 9.0max 37 44.55 447.3MHz 1.85 7.4 2.6 1.0 11.0 10 1.85 BLOCK DIAGRAM Single Channel FSK Transmitter Block Diagram RF SAW Filter Final Amplifier 2nd Amplifier TX Main Interface TX Frequency 447.3MHz Output Power Level 5~10mW Frequency Deviation 2.5kHz Channel Spacing 12.5KHz Channel Bandwidth 8kHz Crystal Oscillator Frequency Modulation TX_DATA
INTEGRATION NOTES POWER SUPPLY REQUIREMENTS The has a low-drop voltage regulator which can deliver a constant 2.8VDC to the module circuitry when the external supply voltage is more than 3.0VDC, with 40dB or more of supply ripple rejection. TX MODULATION REQUIREMENTS The module is factory-set to produce the specified FM deviation with a TXD input to pin 3of 3V amplitude, i.e. 0V "low", 3V "high COMMUNICATION RANGE It is very difficult for us to commit the range obtainable in any given situation, as there are many other variants involved. The main ones to consider are as follows: Type and location of antennas in use Type of terrain and degree of obstruction of the link path Sources of interference affecting the receiver "Dead" spots caused by signal reflections from nearby conductive objects ANTENNA MATCHING Most important for effective data transmission is selection of a good antenna, and RF grounding, both for the transmitter and the receiver. Without a good antenna it is impossible to transmit data over a long distance. The receiver has a SMA connector (a simple antenna input pin) basically. It doesn t require additional antenna matching if you purchase Cellution s antenna as well. If you use a simple antenna input pin, any suitable UHF antenna can be connected to it. If the receiving antenna is installed away from the receiver module, a 50-Ohm coax antenna wire can be used. The shielding of the antenna wire should be soldered to the case near the antenna input of the DRXF-xxx. It is possible, but not recommended to connect the receiver module and the antenna by a connection on a PCB. This will decrease the receiver performance in most cases. In most cases the following basic rules will help you. Connect an antenna with 50-Ohm impedance. Place the antenna vertically, straight up or down from the transmitter and receiver module. Do not cover the antenna with metal parts. The connection of the metal surface of the receiver case to a larger metal part (ground plane) will increase radiation efficiency. Such metal parts should not be placed near the antenna. The human body can have a similar effect to metal objects. Pocket receivers should be held in the hand and held in a position away from the body. Best range is achieved if the transmitter and receiver antenna are in direct line of sight. Any object in between the transmitter and receiver antenna, and metallic objects in particular, will decrease the range. The transmission is influenced by reflections of the transmitter signal on metallic surfaces and building. There is possibility that data errors will occur due to overlapping of the direct and reflected signals. ERROR DETECTION or ERROR CORRECTION PROCEDURE in WIRELESS COMMUNICATION Here are some routine causes of errors that create problems with communication using radio waves, and this section describes briefly how to solve them. With two-way communication, information flows in the direction from device A device B, and the direction from device B device A. But with one-way communication, information flows in the direction from device A to device B only. So Information does not flow from B to A.
With Half duplex method, the transmission of information is carried out in the direction from device A device B, and from device B device A. However, with this communication method, communication is carried out alternately, not simultaneously. With most of this method, the same frequency is used for both transmitter and receiver. With full duplex method, the transmission of information can be carried out in the direction from device A device B, and from device B device A simultaneously. In the tele-control and telemetry system, information is often carried out using one-way communication or half-duplex operation. Communication is by half duplex method with the switching operation between transmitting and receiving. Here simple example by using one-way communication is single-channel FSK transmitter and receiver. And multi-channel FSK transceiver use two-way communication or half-duplex operation. However, complicate data communication systems and most of voice communication systems like a cellular-phone use full duplex method. On the transmission path, there are various possible causes of errors, and in order to transmit the data correctly, line control between the transmitter and the receiver is necessary to control synchronization of timing and errors. Generally, there are data transmission control procedures such as non-procedural, basic control, and high level data link control (HDLC). There are 1:1, 1:N, or N:N in the operations of the radio equipment, these can be applied in two-way communication and data control procedure like HLDLC must be added. Transmission is carried out when just the transmission control code is agreed with the transmitting and receiving end. A user of equipment should consider data control procedure such as the control of errors. Data is transmitted in block units, and if an error occurs, only the block is corrupted. There are two modes; basic mode and extended mode. In basic mode, only text files are transmitted, and when transmitting transparent data (binary data) is transmitted, extended mode is used. While the basic procedure uses character based transmission, HDLC uses bit-oriented transmission in frame units, and concerned with addresses, control codes, information and frame check codes and so on. It is a synchronous flag system in which the start and end of the transmitted frames are flagged. Transmission control is automatic with FCS (Frame Check Sequence) used for error detection. This allows for highly reliable transmission. Data can be transmitted with full transparency. FCS uses the CRC. A system for establishing data links uses with a point-to-point method of connection. The transmitting end sends an enquiry code, and data is transmitted after the receiving end sends acknowledgment to the transmitting end. With a point-to-point system, both devices have an equal relationship. A system for establishing data links uses with a multi-point method of connection. This is a linkage between a control station and subsidiary station. The control station periodically sends requests to send data (data sent to the control station) to the subsidiary stations in the network. If the control station has data to send to a specific subsidiary station, it enquires whether the subsidiary station is able to receive before sending the data. Preamble Start bit Address Control Information (User Data) CRC Stop code With data transmission, for wired (cable) communication as well as for wireless, error control must be implemented. There can not be compared between wireless communication using radio waves and wired communication in terms of the prevalence of causes of errors such as noise, interference, decay, so measuring methods against errors must be put in place. Various methods are possible, but there is always the issue of balancing the level of processing used with the constraints such as application, cost, time, and engineering in design of the system. Normally, we are not afflicted by slight noise or interruptions when we use a mobile phone, and we can come over a bit of flicker on a television screen. High-level error processing is used for the sound in mobile phones, but some errors seem to be inevitable.
However, for data transmissions such as mail, some errors can be fatal. If we consider a industrial equipment controlled by radio, malfunction caused by transmission errors would cause serious and life-threatening accidents, and might involve the loss of important data. As a designer of radio equipment, it is necessary to pay attention to these things not to happen even if errors are occurred. The following two types of error are possible; Random error which occurs randomly without any temporal relationship with other errors, Burst errors that occur suddenly and relatively consecutively. Processing errors in radio communication must be handled at both the hardware and software levels. If appropriate measurements are taken, wireless communication, not inferior to wired communication, can be achieved. For one-way data communication like transmitting and receiving text, sound and images, the following error processing methods are available. If no error processing is used, the system cannot be operated properly. For relatively unimportant data such as the collection of temperature data, where the same data is sent continuously (or it is analog-type data), the frame structure with error detection codes can be used and receiving equipment can decide whether or not there are errors based on this code, and can discard the data if an error is present. Methods of calculating error detection codes include the checksum method, the CRC method and so on. For applications where you want to keep errors to the minimum, use a method such as FEC (Forward Error Correction). This is a system in which the transmitter includes code that allows the receiver to perform error correction. This code makes the transmitted data longer than the actual data, but this method allows us to approach error free transmission. Reed-Solomon code and trellis code are representative types of this kind of code, and there are other types that incorporate these codes. Furthermore, interleaving methods are also used to handle burst errors in radio communication. In addition to FEC for two-way communication system, there are methods that use ARQ (Automatic Repeat Request). With the ARQ system, data is sent as a packet in a frame format, and if an error occurs, the receiver sends a resend request, thus achieving error free data transmission. This is used in most WLANs and other delicate wireless systems. In order to avoid errors, it is necessary to use these protocols for data transmission. Specifically, with packet communication, address information, a packet number, packet size, status/control, frame check and the like is attached to either end of each packet. The receiving end performs error detection, and if necessary sends a resend request, thus achieving error free data transmission. A preamble and start code is attached to the first packet in radio communication that uses packets. There are cases where a preamble is necessary in order to synchronize the radio equipment. With the purpose of detecting data errors in the packet frame, the transmitting end adds a frame check code at the end of the packet when forming the packet. The receiving end then decides whether or not there are errors based on this code, and if it detects a data error, it sends a request to the transmitting end to resend the data, thus achieving error free data transmission. Preamble Start code Receiver address Sender address Packet number Status /control Information (User data) Frame check code Stop code This system includes the checksum method, the CRC method (Cyclic Redundancy Check), the parity check method and so on. The CRC method is better than the checksum method in detecting errors, and it is used in most data transmission protocols such as wireless LANs so on. CRC systems include 5-bit and 12-bit, but currently the most commonly used systems are 16-bit or 32-bit, and in particular, CRC-CCITT and so on is frequently used. With CRC-CCITT the data frame is calculated by dividing by constants, and the 16-bits (2 bytes) of the result are attached for transmission at the end of the data. The receiving end performs a similar operation, and if the result is correct, it determines that there is no error in the data transmission. If not, it determines that there is an error and sends a resend request. To explain in rather more detail, in the CRC operation at the transmitting end, the bit string of the
frame data is treated as a numerical value (this is called the message polynomial), and the message polynomial is divided by a generator polynomial (constant) X16 + X12 + X5 + 1, and the remainder (CRC code: 2 bytes) is attached to the end of the data for transmission. This operation can be performed by the CPU software, but if high speed processing is necessary, it is performed using hardware. Some CPUs contain hardware for this CRC operation, while other CPUs form packet data frames (HDLC function). If the situation permits, it is conceivable to use FPGA or gate arrays, including peripheral equipment. In the transmission path of wireless communication there may be noise and interference that causes loss, so that the code pulse is distorted, and discriminating between data becomes hard. In the receiving equipment a clock signal for synchronization is required for decoding the data, but it is necessary to extract this from the received data stream. The base band signal normally uses NRZ code, but at the transmitter end if this is directly input to a modulator as a base band signal, with data that is a sequence of 0s or 1s, the receiver cannot duplicate the synchronizing clock from the signal (clock recovery). In order to overcome this problem, means such as the use of Manchester code are available. As shown in the diagram below, with Manchester code the middle of the code always reverses polarity, so that unbroken strings of 0's or 1's are avoided, and clock recovery for the receiver is simplified. However, compared with NRZ code, using Manchester code makes the occupied frequency band wider. The Never-fail means that even if some interference occurs, the software or hardware exercises control tends in the direction of safety. It is a safety philosophy that seeks to limit any damage to the minimum. This is implemented in all fields of design, including construction, electricity and the like. Especially compared with other technologies, the likelihood of errors arising with products using radio waves is high. However it s quite difficult to achieve perfect error processing, we cannot guarantee that there will be no errors at all. Please remember that it is necessary to implement Never-fail thinking with regard to the system overall.
INTERFACE EXAMPLE (*refer to Interface Method Guide or Development Kit Guide ) A typical interface is shown in the below figure. Please ask Cellution dealers or technical support for RS-232C or UART interfaces. FSK RF Module Interface Method Serial Interface (UART) RS232 Driver IC Control CPU UART Interface RXD TXD TX Interface TX Module(DTXF) 2.8V Operation TX_D TX_D ISP(or SPI) download interface JTAG download interface RX Interface Display part (optional) Busy RSSI TX RX Mode Setting Part (optional) Test/Modem mode RX/TX Data Rate 3.0~5.5V(DC) RX_EN RSSI RX_D RX_A Power Supply Part 5.5~12V(DC) Regulator
TEST SCENARIO PC-to-PC communication 1. Supply power (5V DC/AC to 12V DC/AC) to the development kit. 2. Connect antenna to the SMA connector in the RF module. 3. Connect RS-232C cable to PC(Set Modem ) 4. Install the bundle application program (SerialWorks) into your PC (Windows 98 SE, Windows CE.NET, Windows 2000, XP) and set a COM port and the BAUD RATE : 19,200bps(factory default), the STOP BIT : 1, the PARITY : NONE **You d better set the SerialWorks at the HEX mode 5. Try to transmit and receive USER data for testing (Max. user data: less than 200 Bytes, Min. user data: more than 4 Bytes) Equipment test FSK RF Module Test Method HP8920A RF Communication Test Set Screen Crontrol Instrument State Power RF IN/OUT User Data Funtion Data 7 8 9 Curser Control 4 5 6 1 2 3 + 0. / - Audio Ant(TX) TX_D TX Module(DTXF) 1. Supply power (5.5V DC/AC to 12V DC/AC) to the development kit 2. Connect the TNC-to-SMA cable between the SMA connector in the RF module and the equipment 3. Set Test Mode 4. There are the TX ON/OFF & RX ON/OFF switches on the development kit. Switch on/off before your testing 5. Set the data rate, CW or 1000bps for TX / Set the baud rate, 1000bps for RX